Method of Preparation of a Monolithic Catalyst for Selective Catalytic Reduction of Nitrogen Oxides

Abstract

Method of preparing a monolithic SCR catalyst with a plurality of gas flow channels comprising the steps of (a) providing a monolithic shaped substrate with a plurality of parallel gas flow channels; (b) coating the substrate with a washcoat slurry comprising titania; (c) drying and calcining the washcoat slurry; (d) impregnating the dried and calcined washcoat with an 10 aqueous impregnation solution comprising a precursor of a vanadium oxide; (e) drying the thus coated and impregnated washcoat at a drying rate of 5 mm/min or less along flow direction through the gas flow channels; and 15 (f) activating the dried, coated and impregnated washcoat by calcining.

1 . A method of preparing a monolithic SCR catalyst with a plurality of gas flow channels comprising the steps of
 (a) providing a monolithic shaped substrate with a plurality of parallel gas flow channels;   (b) coating the substrate with a washcoat slurry comprising titania;   (c) drying and calcining the washcoated substrate;   (d) impregnating the dried and calcined washcoated substrate with an aqueous impregnation solution comprising a precursor of a vanadium oxide;   (e) drying the thus coated and impregnated washcoated substrate at a drying rate of 5 mm/min or less; and   (f) activating the dried washcoated and impregnated substrate by calcining.   
     
     
         2 . The method of  claim 1 , wherein the drying rate is controlled by controlling a drying air flow rate to 0-3 m/s and a drying air temperature of below 70° C. 
     
     
         3 . The method of  claim 1 , wherein the drying of the washcoated and impregnated substrate is performed by means of micro wave or long wave heating. 
     
     
         4 . The method of  claim 1 , wherein the drying of the washcoated and impregnated substrate is performed by placing the substrate in a position horizontally relative to gravity. 
     
     
         5 . The method of  claim 1 , wherein the aqueous impregnation solution further comprises a precursor compound a tungsten oxide. 
     
     
         6 . The method of  claim 1 , wherein the monolithic shaped substrate is composed of a number of corrugated sheets stacked upon each other. 
     
     
         7 . The method of  claim 6 , wherein each of the corrugated sheets are provided with a flat sheet prior to be stacked. 
     
     
         8 . The method of any  claim 1 , wherein the corrugated shaped substrate is formed by rolling up a single corrugated sheet. 
     
     
         9 . The method of  claim 8 , wherein the single corrugated sheet is provided with a flat sheet prior to rolling up. 
     
     
         10 . The method of  claim 6 , wherein the corrugated sheet(s) comprise(s) fiberglass. 
     
     
         11 . The method of  claim 1 , wherein the monolithic shaped substrate is obtained by extrusion of ceramic material. 
     
     
         12 . The method of  claim 1 , wherein the activated substrate of step (d) comprises vanadium pentoxide. 
     
     
         13 . The method of  claim 12 , wherein the activated substrate further comprises tungsten trioxide. 
     
     
         14 . The method of  claim 1 , wherein the monolithic SCR catalyst is in form of a wall flow filter. 
     
     
         15 . The method of  claim 2 , wherein the drying air rate is 0 m/s and the drying is performed at room temperature.